Study on an after-laying test for a long-distance GIL

Technologies for the after-laying test of a long-distance gas insulated transmission line (GIL) have been developed for the detection of partial discharge (I’D) and contact defects. We constructed long (168 m) test line in a deep tunnel and clarified the propagation characteristics of PD signals through the GIL as well as the spatial sensitivity and S/N characteristics of PD sensors for locating metallic particles. We have also proposed the application of a fiber-optic temperature distribution sensor for locating contact defects and confirmed the validity of this sensor for the GIE test line.